A good and standard surgical face mask has three layers. The outer, first or coloured layer is regarded as the fluid-repelling layer (hydrophobic).
This layer primarily prevents any fluids from gaining access into the nose mask.
Next is the middle layer that basically serves as the barrier or hindrance to germs, it is more like the filter.
It does the primary job of trapping germs, bacteria and viruses particles that might have escaped the first layer.
The innermost or last layer is the moisture-absorbing layer. The innermost layer absorbs fluids when we cough, sneeze or talk.
It is able to absorb particles from the mouth of an infected person as ensures that they don't infect others.
Any surgical mask that doesn't have these three basic layers is substandard and cannot be used to protect against any infection like corona virus that is transmitted through respiratory droplets.
Now, how will you feel that you are talking and then all the particles coming out of your mouth is landing against the fluid repelling (coloured) layer instead of the moisture absorbing layer.
Your mouth and nose will be virtually be in contact with most of all the particles coming out of your mouth since the coloured is repelling fluids and does not absorb them.
Qualities that determines a standard mask in addition to the above
It does not matter what the goal is; to prevent outward or inward transport of dangerous particles, more emphasis is placed on the fact that the filter of the mask or respirator must be able to capture all range of dangerous particles usually within the range of (less than 1 to greater than 100micro meters) over a range of air flow (10 - 100L/min).
A quality face mask is determined by its pore size, efficiency and filtration rate. The pore size of the mask on its own determines the efficiency of the filtration rate of the mask.
Another factor is the rate of air resistance by the face mask, a quality face mask is expected to have some degree of air resistance and pressure drop.
This quality ensures that bio-aerosol or respiratory droppings doesn't have easy and direct access through the pores of the face mask.
Not every mask are suitable and effective in preventing various bio-aerosols especially some viruses that are very small in size.
Generally, the pore diameter of most surgical mask ranges from 16 - 51 microns.
Any bio-aerosol less than 16 microns will definitely pass through the micro pores of the mask.
Hence the need to know the suitable and quality mask for infectious diseases.
Mask with lesser pore size are much more effective and they have higher filtration rate when compared with those with higher pore size.
The quality of a mask should never be ignored. Always go for those masks with lesser pore size.
The inner layer or white side of the mask is designed to contain, absorb and filter droplets of microorganisms that are released from the mouth and nasopharynx of an infected person.
So when infected or probably you sneeze and cough, you are expected to put on the face mask to prevent you from infecting or spreading the disease to others.
Mechanism of filtration in standard surgical mask and respirators is quite complex but I will make it as simple as it can be as usual.
The type of filters in most modern surgical mask and N-respirators are fibrous in nature. They collet particles through three mechanical ways namely:
•Inertial impaction
•Interception and
•Diffusion
These three mechanical mechanisms work to ensure that particles are captured appropriately.
The inertial impaction and interception both work together to primarily capture larger particles while diffusion is responsible for capturing of smaller particles.
Some times, the filters could be made of charged fibers thus making them to operate based on electrostatic attraction (with particles of opposite charges getting attracted to the mask).
With the electrostatic charges in action, it makes it easier for it to capture both larger and smaller particles.
At any point any particle that is oppositely charges passes, they are immediately trapped.
During the stage of inertial impaction, those particles that have high inertial due to their size or mass cannot move along with airstream thus, they are automatically diverted to the filter.
Similar thing happens during interception, larger particles are intercepted when they jam or get closer to the filter fiber but during diffusion, what happens is that, because smaller particles have lesser weights, they are easily bombarded by air wave thus causes them to deviate and come in contact with the filter where they are consequently trapped by strong molecular forces thus, making it very difficult for them to be released.
The myths about proper use of the face mask.
Over some months now, there has been a serious misconception on the proper use of the nose masks.
It is even quite unfortunate that even some of our very own health workers are guilty of this. The misconception is this:
"If one infected with a disease, you are expected to wear the face mask in such a way that the front side (coloured part) faces outside while the white part faces you.
On the other hand if you are apparently healthy, you put it on with the coloured part facing inward while the white part facing outward."
From all indications and findings so far, no regulatory body backs up such claims, WHO and CDC, NCDC and other health regulatory body have never made any public notice or statement to support such practice.
This is the problem you get when some fakes news keeps spreading without governmental agencies quick intervention to dispute and nullify false claims.
As it stands, there is only but one correct way to wear the surgical mask and that is:
"the coloured part facing outside while the white part facing inwards" it doesn't matter if you put it on to prevent being infected by other people or because you are infected and you don't want to infect others."
Nice